82 



ANIMAL ELECTRICITY. 



Both species (Nagwj of Aristotle and Oppian) 

 are abundant in some parts of the Mediter- 

 ranean, and are frequently brought to the 

 market of Rome. Off the west coasts of 

 France, in Table-bay at the Cape of Good 

 Hope, in the Persian Gulf and in the Pacific 

 Ocean, the same, or at least nearly similar 

 species are plentiful. They frequently form an 

 article of food amongst the poorer class in the 

 coast towns between the Loire and the Ga- 

 ronne; but the electrical organs are carefully 

 avoided, as they are supposed to possess some 

 poisonous properties. The Gymnotus is found 

 in several of the rivers of South America ; it 

 was met with by Humboldt in the Guarapiche, 

 the Oronoco, the Colorado, and the Amazon. 

 The Malapterurus (Silurus, of Linnaeus) occurs 

 in the Niger, the Senegal, and the Nile ; the 

 Trichiurus in the Indian Seas ; the Tetraodon 

 has been met with only on the shores of Jo- 

 hanna, one of the Comoro Isles. According 

 to Margrav* there is a kind of ray-shark on the 

 coasts of Brazil, which possesses the power of 

 giving shocks. He described the fish under 

 the name of Paraque.f It is the Rhinobatus 

 electricus of Schneider and other modern ich- 

 thyologists. But in an examination which 

 Rudolphi made of the fish in question, he 

 found no structure resembling that peculiar 

 organ which exists in all the well-known elec- 

 trical fishes. No other naturalist has made the 

 same observation as Margrav, so that the elec- 

 trical power of this fish cannot be regarded as 

 satisfactorily ascertained. In Maxwell's Ob- 

 servations on Congo, mention is made of a 

 large fish " like a cod," possessed of electrical 

 powers, which was taken in the Atlantic Ocean. 

 No such animal has yet come under the notice 

 of any scientific observer. Certain insects 

 seem to be possessed of some power re- 

 sembling animal electricity in its effects, but 

 few observations have hitherto been made on 

 these. Reduvius serrutus is one of the insects 

 so endowed; with regard to which an intel- 

 ligent naturalist reports, that, on placing a 

 living individual on the palm of his hand, he 

 felt a kind of shock, which extended even to 

 his shoulder; and that, immediately after- 

 wards, he perceived on his hand red spots at 

 the places whereon the six feet of the insect 

 had rested.J Margrav described a species of 

 Mantis, a native of Brazil, which, on being 

 touched, gave a shock felt through the whole 

 body. According to the report of Molina 

 and Vidaure,|| when the Sepia hexapodia is 

 seized with the naked hand, a degree of numb- 

 ness is felt, which continues for a few seconds. 

 Alcyonium bursa, a native of the German 

 Ocean, is said to have communicated to the 

 hand a sensation like that of an electrical 

 shock.^]" 



It must be regarded as an extremely interest- 



* Hist, return Nat. Brasil. 1648. 

 t The name Puraqua is used by Condamine in 

 reference to the Gymnotus. 



% Kirby and Spence's Entomol. vol. i. 110. 

 <S Naturgesch. von Chili. S. 175. 

 (I Gesch. dcs Konigr. Chili. S. 63. 

 T Treviranns, Biologie. V. 144. 



ing fact that the electric fishes belong to genera 

 widely removed from one another in structure 

 and habits, and yet that their own structure is 

 not so peculiar as to prevent them from being 

 arranged along with many other fishes posses- 

 sing no degree of the same power and no 

 vestige of a structure analogous to their own. 



As the fishes enumerated above have not all 

 been examined with the same degree of atten- 

 tion, we are ignorant of the extent to which 

 they exhibit phenomena exactly resembling one 

 another. But it is well ascertained that they 

 all agree in possessing the power of commu- 

 nicating a sudden shock to the hand which 

 touches them. This shock causes a certain 

 degree of temporary numbness not only in the 

 finger which immediately touches the fish, but 

 also in the hand, and sometimes even in the 

 arm. The sensation produced has been com- 

 pared by different experimenters to the shock 

 felt on the discharge of a Leyden phial, dif- 

 fering from it only in force. Hence the shock 

 caused by an electrical fish is said to be pro- 

 duced by a discharge of its electricity. The 

 numerous facts relating to the phenomena 

 which accompany or are connected with this 

 discharge, which have been collected by the 

 industry of the many observers of the last and 

 the present age, who have devoted their atten- 

 tion to the subject,* may be conveniently ar- 

 ranged under the following heads: 1. the 

 circumstances under which the discharge takes 

 place : 2. the motions of the fish in the act 

 of discharging : 3. physiological effects of 

 the discharge : 4. magnetical effects of the 

 discharge : 5. chemical effects of the dis- 

 charge : 6. results of experiments on the 

 transmission of the discharge through various 

 conducting bodies : 7. the production of a 

 spark and evolution of heat : 8. results 

 of experiments in which the nerves, electrical 

 organs, and other parts, were mutilated : 9. 

 descriptions of the electrical organs in the 

 several fishes which have been anatomized. 



I. Circumstances under which the discharge 

 takes place. Electrical fishes exert their pecu- 

 liar power only occasionally, at irregular inter- 

 vals, and chiefly when excited by the approach 

 of some animal, or by the irritation of their 

 surface by some foreign body. The discharge, 

 both with regard to time and intensity, seems 

 to be dependent on an exertion of the will. 

 They discharge both in water and in air. 

 Sometimes the discharge is repeated several 

 times in close succession ; at other times, par- 

 ticularly when the fish is languid, only one 

 discharge follows each irritation. The inten- 

 sity of the torpedo's discharge is generally 

 greater when the fish is vigorous, becomes gra- 

 dually less as its strength fails, and is wholly 

 imperceptible shortly before death takes place ; 

 but Dr. Davy has met with some languid and 

 dying fish which exerted considerable electrical 



* Redi, Reaumur, Walsh, Ingenhousz, John 

 Hunter, Cavendish, Bancroft, Spallanzani, Wil- 

 liamson, Humboldt, Gay Lussac, Geoffroy, J. T. 

 Todd, and Dr. John Davy, have all laboured in 

 the same field of inquiry. 



